Pole core

ABSTRACT

A pole core with pole lips serves for fixing a field winding in the pole housing of a direct current motor. The pole core has a central pole body mountable on an inner side of the pole housing. The pole lips are formed of one piece with the central pole body and are resiliently and springily connected to the central pole body, so that the field coil can be pressed against the pole housing in an elastic springy manner without additional spring elements, so that no damage occurs to the insulating coat of the coil.

BACKGROUND OF THE INVENTION

The present invention relates generally to a pole core. Moreparticularly, it relates to a pole core which has pole lips for fixing afield winding in a pole housing of a direct current motor.

In a known pole core (WO 89/06874), pole lips extend from its centralbody along the longitudinal sides of the pole core. The field winding ofthe direct current motor is clamped between the housing inner wall, towhich the pole core is screwed, and the pole lips. In order to avoiddamage to the field winding insulation, a special elastic insulatingmaterial is introduced between the pole core and the winding.Installation tolerances are compensated by the plasticity of theinsulating material and, where applicable, by the coil body insulatingcompound which also provides pre-fixing of the assembled unit, and henceprevents separation of the components.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a polecore which avoids the disadvantages of the prior art.

In keeping with these objects and with others which will become apparenthereinafter, one feature of the present invention resides, brieflystated, in a pole core in which the pole lips are resiliently andspringily connected to a central body of the pole core and press thefield winding against the pole housing.

When the pole core is designed in accordance with the present invention,it has the advantage that it allows high strength insulating coats,which have a much lower plasticity than conventional PVC coats, to beapplied to the field coils.

Due to the resilient connection of the pole lips with the central bodyof the pole core, fitting tolerances can be compensated without the needfor a special insulating body. At the same time, pre-fixing is ensuredduring fitting of the pole core and during the clamping of the fieldwinding, whereby any loosening of the assembled unit is prevented, evenwhen subjected to dynamic loads due to vibrations.

A particularly preferred design of the pole core is one in which thepole lips have a recess or a groove at the transition to the centralbody of the pole core. Stresses on the coil in the edge region areprevented due to the pole lip, in particular when the recess or grooveis arranged on the inside, i.e. the pole lip side which faces the fieldwinding, so that damage to the insulating layer is minimized.

The simple manufacture of the pole core is provided when grooves in thetransition between the central body and the pole lips are producedsimply by material displacement or material removal.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an electric motor with several fieldcoils held by pole cores. One pole assembly is shown in part section;

FIG. 2 shows a part cross-section of an electric motor in accordancewith FIG. 1 with a second design of a pole core in assembled position;

FIG. 3 shows a view of the pole core from the underside;

FIG. 4 shows a section through the second design example of the polecore; unassembled, and

FIG. 5 shows a section through the first design example of a pole core.

DESCRIPTION OF PREFERRED EMBODIMENTS

The perspective representation in accordance with FIG. 1 shows thehousing 1 of a direct current motor 3. The housing wall has four fieldcoils 5 clamped to it by means of associated pole cores 7.

One of the field windings is partly cut away to show that the pole lips11 extend from the central body 9 of the pole core 7 in the region ofthe longitudinal edges of the core, extending over the entire length ofthe central body 9. The pole lips project over the field windings sothat when the pole core is tightened, they are pressed against the innerwall of the housing 1.

The pole cores are held by the fixing screws 13 which are passed throughthe wall of the housing 1 from the outside and screwed into a tappedhole 15 in the central body 9 of the pole cores.

The clamping of the field coils is again clearly shown in the FIG. 2through section II--II in FIG. 1. Identical parts are identified by thesame reference characters.

The pole core 7 is secured by means of the fixing screw 13 which ispassed from the outside through the wall of the housing 1. The fieldcoils 5 are clamped between the pole lips 11, which extend from thecentral body 9, and the wall of the housing 1. The section in accordancewith FIG. 2 shows clearly that recesses or grooves 17 are provided inthe transition between the central body 9 and the pole lips 11 on theside facing the field winding 5 which extend over the entire length ofthe pole lips.

FIG. 3 shows a dismantled pole core 7 viewed from the underside. Thecentrally arranged hole 15 is clearly recognizable.

This is provided with an internal thread in which the clamping screw 13is located. The pole lips 11 which extend from the central body 9 of thepole core 7 are also clearly recognizable. They have a longitudinalgroove 17 in the transitional region between the central body and thepole lips.

FIG. 4 shows a further design example of a pole core 7' which ischaracterized by the fact that two grooves 17'a and 17'b are provided inthe transition between the central body 9' and the pole lip 11'. Thegroove 17'a extends on the inner face of the pole lip which faces theinner wall of the housing 1, as seen in the assembled position, whilethe groove 17'b is arranged on the opposite outer side of the pole lip.

The pole core 7' is provided with a hole 15' which has an internal screwthread to locate the clamping screw 13 (see FIGS. 1 and 2). Tofacilitate the insertion of the fixing screw, the internal screw threadin the pole core can be provided with a pilot hole on the side facingthe inner wall of the housing.

FIG. 5 shows a section through a further embodiment example of a polecore 7", in which the transitional region between the central body 9"and the pole lip 11" does not have a distinctive groove, but merely anotch 17".

The pole core shown in FIG. 5 is also provided with a hole 15" which hasin internal screw thread. To facilitate the insertion of the fixingscrew. This embodiment design can also be provided with a pilot hole onthe side facing the inner wall of the housing.

It should be mentioned that the longitudinal grooves 17 (FIGS. 2 and 3),17'a, 17'b (FIG. 4) and 17" (FIG. 5) can be arranged in any suitablemanner in the transitional region between the central body and the polelips of the pole core. It is possible, for example, to apply a deformingprocedure in order to roll longitudinal grooves in the manner of flutesor to engrave these into the region where the pole lips originate. It isfurther feasible to arrange grooves in the transitional region betweenthe pole lips and the central body of the pole core by means of agrinding or milling process. It is further possible during themanufacture of the pole core 7" or during a casting process, to providenotches 17" such as shown in FIG. 5, which result in some materialweakening.

The pole core design which is described here makes it possible to clampfield windings of electric motors to the wall of the motor housing, freefrom any damage, even when the insulating material selected for thefield coils is a very brittle heat resisting coating. In such coils,manufacturing tolerances can no longer be compensated by the plasticityof the insulating material; but the resiliently springy pole lips makeit possible for coils to be securely mounted, even for coils providedwith brittle insulating material. Depending on the pole core material,the recesses in the transitional region between the central body and thepole lips can be selected so that the remaining residual materialfacilitates a predetermined spring or clamping force. In such anarrangement, a limit of the forces acting on the field coil can bespecified, thereby virtually eliminating any cracks due to excessiveclamping forces.

The representation in FIG. 2 clearly shows that, particularly in thearrangement of the groove 17 on the side of the pole lip 11 which facesthe field winding 5, any loading of the edge region of the coil byclamping forces is avoided. This region in particular could otherwise besubject to very high clamping forces leading to damage or chipping ofthe insulating material.

The wall thickness which exists in the region of the transition betweenthe central body and the pole lips, i.e. in the region of the grooves,can be arranged in relation to the pole core material, so that areversible preloading results. This means that, if required, the polecore can be re-used after dismantling. Alternatively, it is possible tobend pole lips by stamping prior to assembly. On tightening of the polecores, the pole lips are restored to the required assembly position.Overall, it can be seen that the resilient, springy pole lips, make itpossible to use coils with a thermally stable, harder, insulating coat.Moreover, larger dimensional deviations in the fitting of such coils canstill be tolerated.

The method of rolling grooves into the pole lips or stamping flutes intothese can be used in the case of both conventional poles with lateralpole shoes and poles with frontal pole lips.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofconstructions differing from the types described above.

While the invention has been illustrated and described as embodied in apole core, it is not intended to be limited to the details shown, sincevarious modifications and structural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can, by applying current knowledge,readily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this invention.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims.
 1. A pole core for a direct currentmotor having a pole housing and a field winding, said pole corecomprising a central pole body mountable on an inner side of the polehousing; and pole lips which are formed of one piece with said centralpole body and extend from opposite sides of said central pole body so asto press the field winding against the pole housing, said pole lipsbeing resiliently and springily connected with said central pole body sothat the field winding can be pressed against the pole housing in anelastic springy manner by said pole lips which are resiliently andspringily connected with said central pole body, without additionalspring elements.
 2. A pole core as defined in claim 1, and furthercomprising a transitional region between said central pole body and saidpole lips, said transitional region having two sides and being providedwith a groove on one of said sides.
 3. A pole core as defined in claim2, wherein said transitional region is provided with another groove onanother of said sides.
 4. A pole core as defined in claim 1, whereinsaid central pole body has two longitudinal sides, said pole lipsextending along both said longitudinal sides of said central pole body.5. A method of producing a direct current motor having a pole housingand a field winding, the method comprising the steps of making a polecore having a central pole body and pole lips formed of one piece withsaid central pole body and extending from opposite sides of said centralpole body so that said pole lips are connected resiliently and springilywith said central pole body; and arranging said pole core so that thepole lips which are resiliently and springily connected with saidcentral pole body, press the field winding against the pole housing inan elastic springy manner without additional spring elements.
 6. Amethod as defined in claim 5, and further comprising providing a groovein a transitional region between the central pole body and the pole lipsso as to provide the resilient connection of the pole lips with thecentral pole body.
 7. A method as defined in claim 6, wherein saidproviding includes manufacturing the groove by a material displacement.8. A method as defined in claim 6, wherein said providing includesmanufacturing the groove by a material removal.
 9. A direct currentmotor, comprising a pole housing; a field winding arranged in said polehousing; and a pole core having a pole housing and a field winding, saidpole core comprising a central pole body mountable on an inner side ofthe pole housing and pole lips which are formed of one piece with saidcentral pole body and extend from opposite sides of said central polebody so as to press the field winding against the pole housing, saidpole lips being resiliently and springily connected with said centralpole body so that the field winding is pressed by said pole lips whichare resiliently and springily connected with said central pole body,against the pole housing in an elastic springy manner without additionalspring elements.